Commercial siloxane polymers are generally produced by the hydrolysis and condensation of hydrolyzable organosilicon compounds. The hydrolysis generates a mixture of linear and cyclic polysiloxanes. Depending upon demand, some polysiloxanes produced are more valuable than others. For example, cyclic polysiloxanes may be more valuable than the linear polysiloxanes. Thus, means of encouraging the production of cyclic over linear polysiloxanes in the hydrolysis and condensation of hydrolyzable organosilicon compounds process have been developed. Examples of such processes are described in U.S. Pat. No. 3,983,148, U.S. Pat. No. 4,423,240, U.S. Pat. No. 4,772,737, and U.S. Pat. No. 4,412,080. However, the influence that these processes have over the product is limited.
In addition to methods of influencing the products formed in the hydrolysis and condensation of hydrolysable organosilicon compounds, methods have also been reported to produce cyclic polysiloxanes from linear organopolysiloxanes. These processes include the acid- or base-catalyzed thermal cracking or depolymerization of diorganopolysiloxanes. However, these processes have associated issues such as high reaction temperatures, long reaction and/or equilibration times, high corrosiveness, and high polymer branching.
Processes have also been developed to redistribute cyclic polysiloxanes to produce different ring sizes. Examples of these processes are described in U.S. Pat. No. 4,556,726, U.S. Pat. No. 4,764,631, and EP 0 552 925. However these processes have associated issues such as requiring the separation of the cyclic polysiloxanes from the hydrolysis and condensation product prior to conducting the process, requiring high temperatures, poor control of the ring size polysiloxane produced, or low tolerance for variation in the starting polysiloxane composition. Thus, there exists a need for a process to redistribute polysiloxanes that addresses these issues. There exists a need for a process that does not require separation of the polysiloxane produced in the direct process prior to conducting the process and that can tolerate variation in the starting polysiloxane composition, that allows control of the ring size polysiloxane produced according to the process, and may be conducted at lower temperatures.
The present inventors have developed a method to redistribute cyclic and linear polysiloxanes. In particular, the inventors have found that specific ring-size cyclic and specific molecular weight linear polysiloxanes may be produced by contacting and heating i) a surfactant, ii) an aqueous hydrochloric acid solution, and iii) a silicone, wherein the silicone is silicone hydrolysate, D5, or D6.